Considering this was always failing before, maybe this fixed it?
commit 1043c09ccbcba8e5c2ec5f2a358a442346348bd8
Author: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date: Tue Sep 19 13:31:13 2017 +0200
tests/kms_cursor_legacy: Do not start collecting CRC after making FB busy
Collecting CRC may force a modeset, which is a bad idea after we just
forced a hang. The hang is intended to make sure the page flip doesn't
complete before the cursor, making sure that works.

(In reply to Maarten Lankhorst from comment #5)
> Considering this was always failing before, maybe this fixed it?
>
> commit 1043c09ccbcba8e5c2ec5f2a358a442346348bd8
> Author: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Date: Tue Sep 19 13:31:13 2017 +0200
>
> tests/kms_cursor_legacy: Do not start collecting CRC after making FB busy
>
> Collecting CRC may force a modeset, which is a bad idea after we just
> forced a hang. The hang is intended to make sure the page flip doesn't
> complete before the cursor, making sure that works.
Looks like it, indeed! I'll close the bug now and archive the issue.